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Ensuring a self-sustaining supply of tritium for use in future reactors is one of the key challenges for the fusion community. Software being developed by CCFE scientists could speed up the design of components that will produce tritium in fusion powerplants.

For reactors based on the tokamak concept, a fuel mix of deuterium and tritium is seen as ideal; it fuses at a relatively low temperature and its energy yield is larger than other fusion reactions. Unlike deuterium (extracted from seawater) though, tritium is not naturally abundant and will need to be manufactured.

Breeder blankets are currently being designed that will produce sufficient tritium to power full-scale reactors. These blankets – which will occupy a large amount of the interior of the DEMO prototype powerplant – will contain lithium, which, when bombarded by neutrons from fusion reactions, produces tritium.

Currently the design of breeder blankets (indicated in green in the image) is enormously time-consuming. But thanks to the development of innovative software, the lengthy and costly process of optimising the tritium breeder blanket design is being gradually reduced.

The software has been developed by EUROfusion Engineering Research Fellow, CCFE's Jonathan Shimwell, and allied with the power of supercomputers, means the process of achieving the best parameters for the blankets has been fast-tracked. Such technology can achieve the creation of detailed 3D models of the breeder blanket designs.

Jonathan said: “It is only possible to buy tritium in grams, yet we would need kilograms for an energy-producing fusion reactor. The ITER experiment will be the first machine to test breeder blankets inside a reactor and will provide an excellent comparison for our software simulations.

“The current demonstration reactor designs it looks like we will need hundreds of breeder blanket modules. That is a large increase from ITER and a lot of blankets!”

Animation: A future fusion reactor design with breeder blankets. The animation begins at the top of the reactor and works its way down. It then shows segments of the reactor from the front before moving to the rear. It was created by Jonathan Shimwell to ensure correct geometry.

Using the Breeder Blanket Model Maker software, it is possible to generate blanket models with various geometries and material specifications. Tritium production for each of the models can then be calculated using Monte Carlo computer simulation software. Other performance metrics such as temperature distribution and material stress can also be discovered.

The model input parameters, along with the resulting performance, are then entered into a machine learning algorithm developed by UKAEA's Chris Bowman. This allows an even more optimal design to be found.

Jonathan added: “The combined use of CAD-based parametric modelling and cloud computing is a modern and highly effective approach to solving this tritium production challenge.

“Exciting prospects lie ahead; the creation of CAD models will drive future diverse scientific exploration and facilitate the mapping of data from one domain to another. Cloud computing will allow simulations to be performed on a large scale.

“Effective research requires us to be able to simulate a multitude of design permutations to ensure the most effective design is found. A fully automated approach is highly advantageous.”

The intention is that breeder blankets should, in the future, be capable of surviving and functioning in DEMO for up to five years.

Getting the blanket parameters right – and making the most of innovative technological developments to do this – could provide the key to ensuring the supply of one of fusion's key commodities.

Main image: Cross-section of a future fusion reactor with accompanying breeder blankets. The blankets are shown in green on the interior of the vessel, while the plasma is purple